1. Field of the Art
It is well known that Mo-Bi composite oxide catalysts are useful for selective reactions such as vapor phase catalytic oxidation reactions for producing acrolein from propylene or methacrolein from isobutene or tertiary-butanol, a vapor phase catalytic ammoxydation reaction for producing acrylonitrile from propylene or methacrylonitrile from isobutene, and a vapor phase catalytic oxidative dehydrogenation reaction for producing butadiene from butene. It is also well known that these catalysts have widely been put to practical use on an industrial scale.
2. Prior Art
Accordingly, many patent publications with reference to the compositions of Mo-Bi composite oxide catalysts in these various reactions and the processes for producing them are also well known. A part of such publications are: Specifications of Japanese Patent Examined Publication Nos. 3670/64, 1645/73, 4763/73, 17253/73, 3498/74, 41213/80, 14659/81, 23969/81, 52013/81 and 26245/82; and those of Japanese Patent Unexamined Publication Nos. 503/73, 514/73, 52713/73, 54027/73, 57916/73, 20610/80, 47144/80, 84541/80, 76541/84 and 122041/85.
In these patent publications, there are disclosed the addition effects of an alkali metal and/or Tl, but these trace components are handled without any description for their reaction mechanism or the difference between these metals.
Furthermore, all of the aforementioned patent publications relate to Mo-Bi composite oxide. However, all but Japanese Patent Unexamined Publication Nos. 47144/80 and 76541/84, which disclose the preliminary production of a Mo-Bi or W-Bi composite in the course of producing the composite oxide catalysts, use bismuth nitrate as a raw material of Bi in Examples, and in fact, a water soluble bismuth compound, viz. bismuth nitrate or a hydroxide thereof is recommended also in their descriptions. For the purpose of homogeneous dispersion of Bi in the composite oxide catalyst, this indication may be considered acceptable.